Resonator silencer



" Sept. 17. 1940- ,E. E. WILSON 2,214,894

RESONATGR SILENCE a Filed Dec 12, 1956 2 Sheets-Sheet 1 Sept.-l7, 1940. E. E. WILSO 2,214,894

v RESONATOR SILENCER Filed Dec. 12. 1936 2 Sheets-Shea. 2

fares? 117M907? Patented Sept. 17, 1940 UNITED-- STATES I 2,214,894 RESONATOR smnnosa- Ernest E.- Wilson, General Motors Proving Ground, near Milford, Micln, assignor to General Motors Corporation, Detroit, Mich.,

7 Delaware a corporation of Application December 12, 1936, Serial No. 115,470 8 Claims. (Cl. 123-498) To attenuate the objectionable sound waves which occur in the intake and exhaust systems or internal combustion engines, resonator silv encers, such as those disclosed in my prior applications-Serial Nos. 470,700 and 633,265 which were filedon July 25, 1930 and September 15, 1932, respectively, are now \commonly used. However, because the natural frequencies of the resonators incorporated in these silencers are l fixed and objectionable sound waves of different frequencies may occur in the intake or exhaust system of an internal combustion engine when it is operating at different speeds but not simultaneously, it is frequently necessary, in order to attenuate all of the objectionable sound waves which occur in the intake or'exhaust system of an internal combustion engine, to'provide in it one or more resonators which are operative only when the engine is operating at some speed or speeds and another or other resonators which are operative only when the engine is operating at another speed or other speeds.

The principal object of this invention is to provide an internal combustion engine with a reson- 5 ator silencer in which it is not necessary, in order to attenuate all of the objectionable sound waves which occur in the intake or exhaust system of the engine to which the silencer is applied, to provide in the silencer any resonators which are not operative simultaneouslyandthus to minimize the number oi resonators in the silencer. g A

To attain this object, I provide a silencer with a resonator whose natural frequency may be varied and means for varying the natural frequency of the resonator in accordance with variations in the frequency of objectionable sound waves which occur in the intake or exhaust system of the engine to which the silencer is ap- 0 plied. To render the natural frequency of the resonator variable, the acoustical conductivity of its neck or necks or any of them and/or the volume of its chamber or chambers or any.oi them may be made adjustable. To adjust the acoustical conductivity of the neck or necks and/or the volume of the chamber or chambers a manually adjusted instrumentality and/or any? instrumentality whose movement aiIects 'or, is

. affected by variations in the speed of the engine may be employed. i

For a better understanding of the objects and nature of this invention, reference is made to .the following'specification in'which there are as described the embodiments of my invention resonator silencers in accordance with this inwhich are illustrated in the accompanying drawings. r In the accompanying drawings:

Figures 1 and 2 show internal combustion engines equipped with resonator intake and ex- 5 haust silencers in accordance with this invention.

Figures 3 to 9 are longitudinal sections through yention. 10

The internal combustion engines i0 which are shown in Figuresl and 2 are equipped with intake manifolds ii to which there are connected carburetors l2 and exhaust manifolds 13 to which there are connectedexhaust pipes l4. To the 15 air intake tube of the carburetor of the engine shown in Figure 1, there is connected a resonator'silencer I5 01 the type shown in 'FiguresB to 7 and 9. To the air intake tube oi! the carburetor oi the engine shown in Figure 2, there is 129 connected a resonator silencer 16 of the type shown in'Figure 8. To the exhaust pipe of each of the engines shown in Figures 1 and 2, there is connected a resonator silencer l! which includes a unit oithe type shown in Figures 3 to 7 and 9.

Each of the silencers shown in Figures 3 to 9 includes a cylindrical shell 10 with heads 1i and 12 secured over its ends and a ductthrough which gases may pass through the silencer. The

duct is coaxial with the shell 10 and consists of two tubes of which one extends into and is sufliciently smaller than the other that the overlapping portions of the tubes are separated by an annular aperture. One of the tubes is secured in cache! the heads H and 12. The shell 10, its heads 'H and 12 and the tubes define a compartment which communicates with the duct defined by the tubes through the aperture between the overlapping portions of the tubes.

The smaller of the tubes which define the duct 0 of the silencer shown in Figure 3 consists of two partly telescoped tubular elements 13 and 14-, of which the former is secured in the head 12. and terminates short of the larger tube 15. The tubular element 14 extends beyond the inner end of the tubular element 13 into the inner end of the tube 15 and may be shifted back and forth lengthwise of the, silencer to vary the overlap between the tubes 13-14 and 15. To shift the tubular element 14, there is provided a rod 16 5o which extends through a guide in the head 12 and whose inner end is secured to the tubular element.

The compartment defined by the shell 10, its 1 heads H and 12 and the tubes 13-14 and 15 conthe resonator, may be varied by shifting the tubular element I4.

Within the compartment defined by the shell I0, its heads II and I2 and the tubes and 8| which define the duct of the silencer shown in Figure 4, there is disposed a false head 82 which encircles the tube BI and may be shifted lengthwise of the silencer. On the inner and outer edges of the false head 82, there are formed an nular flanges 83 and 84 which fit snugly around the tube BI and within the shell I0, respectively. To shift the false head 82, there is provided a rod 85 which extends through a guide in the head I2 and whose inner end is secured to the false head. 1

The compartment defined by the shell I0, its head II, the false head 82 and the tubes 80 and 8I constitutes the chamber and the annular aperture 86 between the tubes 80 and BI the neck of a simple resonator.-- The acoustical conductivity of the neck is, of course, fixed but 'the volume of the chamber and, thus, the natural frequency of the resonator, maybe varied by shifting the false head 82.

The compartment defined by the shell I0, its heads 'II and I2 and the tubes 90 and SI which define the duct of the silencer shown in Figure 5 is divided lengthwise into two chambers 82 and 83 byan annular partition 94 which encircles thetube 9| and is secured to it and .the shell. Through the partition 94, there extends a tube which consists of two partly telescoped tubular elements and 98 and interconnects the chambers 92 and 93. The tubular element 95 is se-' cured in the partition 94 and the tubular ele-v ment 96 may be shifted lengthwise of the tubular element 95 to vary the effective length of the tube 95-96. To shift the tubular element 55, there is provided a rod 91 which extends through a guide in the head I2 and whose inner end is secured to the tubular element 96. The chambers 92 and 93 constitute the chambers and the tube 95-46 and the annular aperture 98 between the tubes 90 and ill the necks of a compound resonator. The volumes of the chambers and the acoustical conductivity of the neck 98 are, of course, fixed but the acoustical conductivity of the neck 9586 and, thus, the natural frequencies of the resonator, may be .varied by shifting the tubular element 96.

Within the compartment defined by the shell I0, its heads II and I2 and the tubes I00 and IN.

which define the duct of the silencer shown in Figure 6, there is disposed a partition I02 which encircles the tube I 0| and may be shifted lengthwise of the silencer. On the inner and outer edges of the partition I02, there are formed annular flanges I03 and I04 which fit snugly around the tube IOI and within the shell I0, respectively.

*0! a compound resonator.

of a compound resonator. Thel acoustical conductivities of the necks are, of course, fixed but the volumes of the chambers and, thus, the natural frequencies of the resonator, may be varied by shifting the partition I02.

The larger of the tubes which define the duct 01 the silencer shown in Figure 7 consists of two partly telescoped tubular elements I I0 and I I I, of which the former is secured in the head 'II and terminates short of the smaller of the tubes H2. The tubular element III extends beyond the inner end of the tubular element H0 around the inner end of the tube H2 and may be shifted back and forth lengthwise of the silencer to vary the overlap between the tubesIIO-I II and H2. The compartment defined by the shell I0, its head's II and I2 and the tubes IIO--III and H2 is divided lengthwise into two chambers the shell. In'the partition H5, there is secured a tube II 6 which interconnects the chambers II 3 and H4. Within the chamber H3, there'is disposed a false head I II which encircles the tubular element I I0 and whose inner edge is joined to the outer end of the tubular element II I and may be shifted WIth fl; lengthwise of the silencer. On the outer edge of the'false head I I1, there is formed an annular flange H8 which fits snugly .within the shell '10. To shift the tubular element III and the false head I", there is provided a rod H9 which ex'tends through guides in the head I2 and the partition H5 and whose inner end is secured to the false head.

The chambers I I 3 and I I4 constitute the chambers and the tube H6 and the annular aperture I20 between the tubes I I0I I I and. H2 the necks The volume of the chamber I I4 and the acoustical conductivity of the neck I I0 are, of course, fixed but the volume of the chamber H3 and the acoustical conductivity of the neck I20 and, thus, the natural frequencies of the resonator, may be varied by shifting the member IIII I'I--I I8.

The compartment defined by the shell 10, its heads II and I2 and the tubes I2I and I22 which 'define the duct of the silencer shown in Figure 8 is divided lengthwise into. two chambers I23 and I24 by an annular partition I25 which encircles the smaller of the tubes and is secured to it and the shell. In the partition I25, there is secured a tube 126 which interconnects the chambers I23 and I24. Through the head I2, there extends into the chamber I24 a tube I21 which terminates near the lower side of the shell 10 and through which a liquid may be introduced into or withdrawn from the chamber I24.

The chambers I23 and I24 constitute the chambers and the tube I26 and the annular aperture I28 between the tubes I2I and I22 the necks of a compound resonator. The acoustical conductivities of the necks and the volume of the chamber I23 are, of course, fixed but the effective volume of the chamber I24 and, thus, the natural frequencies ofthe resonator, may be varied by introducing liquid into or withdrawing liquid from the chamber I24 through the tube'IZ'I.

The larger of the tubes which define the duct of the silencer shown in Figure 9 consists of two partly telescoped tubular elements I 30 and I3I of which the former is secured in the head 'II and extends well beyond the inner end 'of and en= circles the smaller of the tubes I22. Within the compartment defined by the shell I0, its heads Ii-and I2 and the tubes I80-I3I and I22, there is disposed 5. false head m which encircles the tubular element I30 and may be shifted lengthwise of the silence'r. To shift the false head I33,

and I36 whichfit'snugly around the tubular ele-.

ment I30 and within the shell 10, respectively. The compartment defined by the shell 10, its head 12, the false head I33 and thetubes I 30I3I and I32 is divided lengthwise into three chambers I31, I38 and I39 by annular partitions I40 and HI which encircle the tubular element I30 and are secured to it and the shell. The partition I40 is imperforate but there is secured in the partition I4I a tube I42 which connects the chamber I38 with the chamber I39 which communicates with the annular aperture I43 between the tubes I30- I3I and I32 through orifices I44 in the tubular element I30 which may be partially or wholly covered by the flange I35 on the false head I33. The tubular element I3I of the tube I30-I3I, whose outer end is of smaller diameter than its inner end but of considerably larger diameter than the tube I32, extends beyond the tubular element I30 and may be shifted lengthwise of the silencer to vary the overlap between the tubes I30-I3I and I32. To shift the tubular element I3I, there is provided a rod I45 which extends through guides in the head H, the false head I33 and the partitions I40 and HI and whose inner end is secured to the tubular element I3I.

The chambers I38, I39-and I31 constitute the chambers and the tube I42, the orifices I44 and the annular aperture I43 the necks of a complex resonator. The volumes of the chambers I38 and I31 and the acoustical conductivity of the neck I42 are, of course, fixed but the volume of the chamber I39 and/or the acoustical conductivities of the necks I44 and I 43 and, thus, one or more of the natural. frequencies of the resonator, may be varied by shifting the false head I33 and/or the tubular element I3 I The silencers shown in Figures 3 to 9 were de signed for installation on an internal combustion engine in the manner in which the silencers I5 and I6 are installed on the engines shown in Figures 1 and 2, i. e., with the outer ends of the larger of the tubes (15, 80, 30, I00, IIOIII, I2I and l30--I3I) which define their ducts connected to the air intake tube of the carburetor so that the air which enters the carburetor and cylinders of the engine fiows through their ducts in the direction indicated by the arrows in the drawing. But any of the units shown in Figures 3 to 9 may be incorporated in a silencer installed on an engine in the manner in which the silencers I1 are installed on the engines shown in Figures 1 and 2 with its duct disposed so that the exhaust gases of the engine pass through it in the same direction as air passes through it when it is employed as an intake silencer.

In whichever manner the units shown in Figures 3 to 9 are to be installed the resonators will, of course, be so proportioned and dimensioned that when their adjustable elements are in one position they will respond to and attenuate by positions they will respond to and attenuate by resonance objectionable sound waves of another frequency or other frequencies which occur in the intake or exhaust system of the engine while it is operating at another speed or other speeds. To vary the natural frequencies of the units shown in Figures 3 to 'l and 9 the rods (18, 85, 91, I08, II9, I34 and I45) may be actuated manually and/or automatically to shift the adjustable elements of the units. in accordance with the requirements. Automatic actuation of the rods may be effected by suitably connecting them to any element whose movement affects the speed of the engine, such as the throttle valve of the carburetor of the engine, to any element whose position is affected \by changes in speed of the engine, such as an element whose position is affected by an engine actuated governor, by a solenoid which is energized by an engine operated generator or by changes in the pressure or rate of fiow of fluid in any partof the intake system, the exhaust system, the lubricating system or the cooling system of the engine or to any two or more such elements. The rods I34 and I45 of the unit shown in Figure 9 may be actuated synchronously or non-synchronously by the same or different instrumentalities. The liquid employed to vary the efiective volume of the chamber I24 of the unit shown in Figure 8 may be obtained from the cooling system or the lubricating system-of the engine on which the unit is installed or from a supply provided especially for the purpose. Any suitable means actuated manually and/or automatically by elements such as those referred to above may be provided to introduce and withdraw and control the introduction and withdrawal ofthe liquid from the chamber I 24 in accordance with the requirements.

Examples of the instrumentalities that may be employed to vary the natural frequencies of the units shown in Figures 3 to 9 are shown in Figures 1 and 2.

Onthe engine shown in Figure 1, there is mounted to the rear of the intake silencer I5 a horizontally disposed cylinder I8 whose ends are closed by heads I9 and 20. Within. the cylinder I8, there is snugly fitted a piston 2I to which there is secured a rod 22 which extends through a stufiing box in the head I9. The portion of the piston rod 22 which is within the cylinder is encircled by a coiled spring 23 which urges the piston toward the head 20 in which there is a vent 24. The portion of the cylinder between the head I9 and the piston 2I is connected to the intake manifold I I of the engine I0 by a tube 25.

The piston rod 22 is connected to the rod 26 by which the adjustable element of the silencer I5 is shifted by links 21 and 2B which are interconnected by a pivot 29 which is mounted so that it may slide in a slot 30 in the generally horizontally disposed arm of a bell crank 3I which is mounted on a pivot 32 which is mounted on the engine Ill. The other arm of the bell crank 3| which is generally vertically disposed is connected to the linkage by which the throttle valve of the carburetor I2 is moved to change the speed of the engine by a pivot 33 which connects two elements (34 and 35) of the linkage.

To vary the natural frequency of the adjustable unit. of the exhaust silencer of the engine which is shown in Figure 1 there is provided within the exhaust pipe I4 a vane 36 which is mounted on a shaft 31. To the shaft 31.-there is secured an arm 38 which is biased to a v position in which the vane 36 is disposed crosswise of the exhaust pipe by a spring 39 and connected to the rod 40 by which the adjustable element of the adjustable unit of the exhaust silencer is shifted by a pivot 49.

On the engine shown in Figure 2, there is mounted a centrifugal governor in which there is included a shaft 42 which is driven by the engine at a speed proportional to the speed of the engine. The shaft 42 is encircled by a collar 43 which cannot rotate or slide with respect to the shaft and a collar 44 which can slide lengthwise of the shaft. To the collar 43, there are connected by 'pivots 45 which extend at right angles to the shaft 42 elements 46 with weighted arms which extend generally parallel to the shaft and hooklike arms which extend inwardly and engage the inner end of the collar 46. To hold the collar 44 in engagement with the hook-like arms of the elements 46, there is provided a spring M which encircles the shaft and may be adjusted by means of an arm 48. With the exception of the arm 48, the elements of the governor which have been referred to are enclosed within a housing 49 which carries a pivot 50 on which there is mounted an arm 56 which is connected to the collar M so that it is rocked on the pivot 5!! when the collar 44 is shifted lengthwise of the shaft 42.

On the outer end of the intake silencer [6 of the-engine which is shown in Figure 2, there is mounted a cylinder 52 whose ends are closed by heads 53 and 54. On the head 53, there is formed a nipple 55 through which the cylinder is connected to the tube l2'l. In the cylinder 52, there is snugly fitted a piston 56 which is urged toward the head 5% by a coiled spring 5?. To the piston 56 there is secured a rod 58 which extends through a guide in the head 54 in which there is a vent Sufficient oil or other suitable liquid to fill the cylinder 52, the tube IZ'l and the chamber 624 to above the level of the lower end of the tube i2? is introduced thereinto before the silencer is put into operation.

On a pivot Eli which is carried by the engine shown in Figure 2 there is mounted a lever Ei whose ends are connected, respectfully, by pivots 62 and B3 to the piston rod 58 and the rod 40 by which the adjustable element of the adjustable unit of the exhaust silencer ET is shifted. To the lever 59, the arm 5i of the governor is connected by a link 64 and pivots 65 and 66. To the lever 6i, there is also connected by the pivot 62 a manually actuated lint:

When the engine shown in Figure 1 is operating, the position of the piston 2i will vary in accordance with variations in the pressure within the intake manifold H, the position of the bell crank 3| will vary in accordance with variations in the position of the throttle valve of the carbu retor l2 and the position of the vane 36 will vary in accordance with variations in the rate of dis" charge of exhaust gases from the engine. Variations in the position of the piston 2i and the,

bell crank 3i will, of course, shift the adjustable element of the intake silencer l5 and vary its natural frequency or frequencies in accordance with the requirements. Variations in position oi the vane 35 will, of course, shift the adjustable element of the adjustable unit of the exhaust silencer Hand vary its natural frequency or frequencies in accordance with the requirements.

When the engine shown in Figure 2 is operating, centrifugal force causes the weighted arms of the elements 48 to move outwardly and to movethe collar 44 toward the rear of the engine against the resistance of the spring", Variations in the position of the collar 44 will through the arm 5|, the link 64, the lever BI and the rods 58 and 40 shift the piston 56 and withdraw or introduce liquid into the chamber 124 of the intake silencer l6 and vary the position of the adjustable element of the adjustable unit of the exhaust silencer I1 and thus vary the natural frequencies of the intake silencer and the ad-. justable unit of the exhaust silencer in accordance with the requirements. time he desires, the operator of the vehicle in which the engine H] is installed may manually regulate the natural frequencies of the intaze silencer and the adjustable unit of the exhaust silencer by shifting the rod 67.

It will, of course, be understood that although I have described and illustrated my invention applied to the intake and exhaust systems of internal combustion engines, it is also applicable to other devices in which objectionable sound waves of different frequencies occur under different conditions.

I claim: v

1. The combination, with a duct through which sound waves with different characteristics travel at different times, of means for attenuating sound waves which travel through the duct including a silencer and means for automatically varying attenuating characteristics of the silencer in accordance with variations in the characteristics of the sound waves which travel through the duct. I

2. In an internal combustion engine, a duct which communicates with a cylinder of the engine and through which gases and objectionable sound waves of different frequencies travel while the engine is operating at different speeds, a resonator which is arranged as a branch of the duct and includes a chamber and an orifice through which the chamber communicates with the duct, and means by which the natural frequency of the resonator may be varied in accordance with variations in frequency of objectionable sound waves which travel through the duct including an element which occupies diflerent positions at different speeds of the engine.

3. In an internal combustion engine, a duct which communicates with a cylinder of the engine and through which gases and objectionable sound waves of different frequencies travel while the,engine is operating at diiferent speeds, a rescnator which is arranged as a branch of the duct and consists of a chamber and an orifice through which the chamber communicates with the duct, and means by which the natural frequency of the resonator may be varied in accordance with variations in frequency of objectionable sound waves which travel through the duct including an eie-.- me nt whose position is affected by changes in the speed of the engine.

4. In an internal combustion engine, a duct which communicates with a cylinder of the en.- gine and through which gases and objectionable sound waves ofdifierent frequencies travel while the engine is operating under different conditions,- a resonator which is arranged as a branch of the duct and includes a chamber and an orifice through which the chamber communicates with the duct, and means for automatically varying the natural frequency of the resonator in accordance ,with changes in the engine operating conditions so that the resonator will attenuate by resonance sound waves of diflerent frequencies under different engine operating conditions.

However, at any 10 5. In a silencer, a shell, and a duct which extends through the shell and with it defines a compartment which encircles the duct, the duct including two tubes of which one extends into and is radially spaced from the other to define with it an aperture through which the compartment communicates with the duct, one of the tubes being adjustable lengthwise of the duct to vary theoverlap between the tubes and thus the acoustical conductivity of the aperture through which the compartment communicates with the duct.

6. In a silencer, a shell, and a duct which extends through the shell and with it defines a compartment which encircles the duct, the duct including two tubes and an extension which is telescopically related to one of the tubes and encircles and is radially spaced from a portion of the other of the tubes to define with it an aperture through which the compartment communicates with the duct, the extension being adjustable lengthwise of the duct to vary the overlap between it and the tube of which it encircles a portion and thus the acoustical conductivity of the aperture through which the compartment communicates with the duct.

7. In a silencer, a shell, and a duct which extends through the" shell and with it defines a compartment which encircles the duct, the duct including two tubes and an extension which is telescopically related to one of the tubes and is encircled by and radially spaced from a portion of the other of the tubes to define with it an aperture through which the compartment communicates with the duct, the extension being adjustable lengthwise of the duct to vary the overlap between it and the tube which encircles a portion of it and thus the acoustical conductivity of the aperture through which the compartment communicates with the duct.

8. In a silencer, a shell, a duct which extends through the shell and with it defines a compartment which encircles the duct, the duct including two tubes of which one extends into and is radially spaced from the other to define with it an aperturethrough which the compartment communicates with the duct, one of the tubes being adjustable lengthwise of the duct to vary the overlap between the tubes and thus the acous-' tical conductivity of the aperture through which the compartment communicates with the duct, and a partition which is carried by the tube which is adjustablelengthwise of the duct and extends from it to the shell so that it is moved lengthwise of the duct when the tube is adiusted.

ERNEST E. WILSON. 

